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Draft 10/26/2016 Authors: Adler, Renwick, Curtis, Kleinhesselink, Schlaepfer, Kachergis, Manning, Remington, Thacker, Aldridge, Bradley, Poulter Climate Change impacts on big sagebrush populations Introduction Sagebrush covers 120 million acres across 14 western states and 3 Canadian provinces, providing habitat for 357 species of conservation concern in the Great Basin alone. Greater and Gunnison sage-grouse, pygmy rabbits, and sage-thrashers are sagebrush obligates, while many others such as mule deer and pronghorn depend heavily on sagebrush habitats. Sagebrush rangelands have been used for livestock grazing, oil and gas development, mineral extraction, and recreation. About _% of the original distribution of sagebrush has been lost due to conversion to agricultural production or development, or degraded by invasive annuals plants, altered fire regimes, and other anthropogenic disturbances. Populations of many sagebrush-dependent species are declining, triggering petitions to list both species of sage-grouse and pygmy rabbits under the Endangered Species Act, while Gunnison sage-grouse were listed as threatened under the act in 2012. Many sagebrush obligate species are identified as species of conservation concern in State Wildlife Action Plans. Consequently, the emphasis of research and management has shifted from sagebrush eradication to restoration and conservation across the west. Climate change casts considerable uncertainty over sagebrush conservation and restoration efforts. Given predicted changes, will sagebrush decline, persist, or even thrive? Where are management efforts likely to achieve benefits over the long-term? Using “best available science” is a key principle of national efforts to prepare for the impacts of climate change, including policy specific to land management agencies (e.g., Executive Order 13653, DOI Climate Adaptation Plan, USFS National Roadmap for Responding to Climate Change). Research to predict sagebrush responses to changing climate could resolve some of this uncertainty by identifying areas where climate change poses the greatest threat to sagebrush and the many species and ecosystem services that depend on it. This kind of climate change vulnerability analysis can also help decision makers prioritize areas for restoration, conservation, and mitigation, and ensure efficient budget allocations. 3. Rationale for model comparison a. Lots of models, validation difficult, look for a agreement’ b. Different models captures different types of responses c. Consistency in predictions would build confidence 4. Research question: How will big sagebrush populations respond to changes in temperature and precipitation within its current range? 5. Methods (link to online table) a. Scope: Big sagebrush, individual locations across the region, time scales b. c. Characterize GCM projections: warming, little change in precip? Four models: i. Spatial, regional correlations (predicts long-term average cover) ii. Local, temporal correlations (predicts short-term change in cover) iii. Regeneration processes (predicts probability of establishment) iv. Biogeographical and biogeochemical processes (cover) Results Despite considerable variation in predicted changes among models and climate projections, consistent patterns in the predictions did emerge. All four models predict that sagebrush will respond positively to climate change at the coldest locations in the region but will respond negatively at the warmest sites (Fig 1). Furthermore, these negative responses appear confined to fairly small geographic areas, primarily hot sites near the ecotone with hot deserts to the south, and sites receiving very little summer precipitation east of the Sierra Nevada. Across much of the range of sagebrush, our models consistently project weak or positive responses to climate change. We also found evidence that vulnerability to climate change, as predicted by our models, correlates with the resistance and resilience classes that represent threats from annual invasive plants and fire. Almost all of our sites where models consistently predicted negative climate change impacts, and most sites where sagebrush response was uncertain, are located within the low resistance and resilience class. Our models predict that the overwhelming majority of sites in the moderate and high resistance and resilience classes will respond positively to climate change. Implications The most important implication of our results is that concerns about climate change impacts should not preclude investments in sagebrush conservation and restoration. Across much of the current distribution of big sagebrush, the changes in precipitation and temperature projected by current climate models are likely to have weak or even positive impacts on sagebrush populations. Within these areas, land management should continue to focus on other threats to sagebrush habitat, some of which could be exacerbated by warming climates. In the hotter areas where our models predict negative impacts of climate change on sagebrush, some of which have low resistance and resilience to invasions and fire, management should focus on protecting sites with cooler and wetter microclimates where sagebrush is likely to persist. Efforts to promote sagebrush seedling establishment and stand resiliency to disturbances may become increasingly difficult under climate change. These recommendations come with important caveats. First, our study only evaluated climate change impacts on sagebrush within its current range; it cannot address expansion of sagebrush into new areas. Second, our study focused on a single species and did not consider impacts on composition or abundance (cover) of sagebrush understory components such as grass and forbs, which are critical components of habitat suitability for sagebrush dependent species. Given their different life history strategies, grasses and forbs may respond very differently than sagebrush. Finally, and most importantly, we did not evaluate impacts of climate change on cheatgrass distribution and abundance or the probability of fire within sagebrush communities. Increases in either could offset or overwhelm the generally positive effects of climate change on sagebrush cover that our models predict. While some work has modeled potential future distribution of cheatgrass, an important next step is to evaluate the influence of climate change on the invasive grass-fire cycle. For a more complete understanding of this work you are welcome to tune into the webinar, hosted by the Great Basin LCC: Predicting climate change impacts on big sagebrush populations: Diverse models project similar response to rising temperatures Friday, November 4 11:00 AM (PST) To register, click on the link below: http://us5.campaign-archive2.com/?u=2bd190572e12f69862b0ed30b&id=23c41a72a8&e=d5759766f2